The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Prosthetic joints can reduce pain due to arthritis, deterioration, deformation, and the like, and can improve mobility in the joint. Oftentimes, prosthetic joint assemblies include certain implantable prosthetic members that are fixed to the patient's anatomy. For instance, prosthetic hip joint assemblies often include an acetabular cup that is implanted and fixed to the patient's pelvis within the acetabulum. Once properly fixed to the pelvis, a liner may be received by the cup, and a femoral component may be moveably coupled within the liner.
Medical professionals often use impactor tools to implant and fix prosthetic members to the patient's anatomy. In the case of the acetabular cup, for instance, the surgeon may attach the cup to one end of the impactor tool and strike or otherwise apply a load to the impactor tool to drive the cup into the acetabulum. Then, the impactor tool is removed from the cup, leaving the cup in the desired location and orientation within the acetabulum. Fasteners can also be used to further secure the cup to the pelvis.
To ensure that the prosthetic member will be oriented in a desired position during the implantation procedure, the surgeon typically moves the impactor tool to a predetermined orientation relative to the patient's anatomy and applies the load while maintaining the impactor tool at this predetermined orientation. Certain measuring devices (e.g., goniometers, etc.) have been proposed for these purposes. Specifically, in the case of implanting an acetabular cup, the surgeon might orient the impactor tool such that the load axis is at a predetermined inclination angle relative to the median plane of the patient's body and/or such that the load axis is at a predetermined anteversion angle relative to the coronal plane of the patient's body. Thus, as the load is applied to the impactor tool, the cup is driven along and fixed at the predetermined inclination angle and/or the predetermined anteversion angle within the acetabulum.
However, measuring the orientation of the impactor tool in this manner can be tedious, time consuming, inconvenient and inaccurate. For instance, surgeons typically must repeatedly measure the orientation of the impactor tool because applying one or more loads to the impactor tool could move the impactor tool out of alignment with the predetermined orientation. Additionally, the impactor tool can be improperly aligned inadvertently due to human error. Furthermore, the goniometer or other measurement device is oftentimes separate from the impactor tool, and thus, the surgeon may need two hands to hold the impactor tool and measure its orientation. Also, blood, tissue or other matter can obscure the surgeon's ability to read the measurement device, which can lead to inaccuracies.
In addition, it can be difficult to know when the implantable prosthetic member has been driven far enough into bone or other tissue. For instance, a surgeon typically drives the acetabular cup far enough into the acetabulum to seat the cup against cancellous bone. However, it can be difficult to visually confirm that the cup is seated against the cancellous bone, and thus, surgeons typically rely on audible, tactile, or other non-visual cues to know the cup has been properly seated. For example, the surgeon repeatedly applies loads to the impactor tool to progressively drive the cup into the acetabulum until the surgeon hears a sound indicating that the cup is seated against cancellous bone. In other cases, loads are applied to the impactor tool until the surgeon feels a certain degree of bounce-back (i.e., displacement of the tool in a direction opposite to the vector of the impact force on the tool) indicating that the cup is seated against cancellous bone. However, the accuracy of these methods can be improved.